Abstract: For deep beams, the complexity of stress mechanism and the variety of the influence factors complicate its calculation. Due to the existence of the extrusion of longitudinal fiber and the warping of the beam section, the classical bending stress calculation formula can not be adopted simply for deep beam problems. Although that there exist various calculation methods for deep beams, such as series solution method, finite difference method and finite element method, they are too complicated to adopt. Starting from the problem of a half-plane continuum with a concentrated load in elastic mechanics, this article considers the middle of the deep beam and the local part of the support as a half-plane continuum with a concentrated load. The influence of bending stress caused by the concentrated load is also taken into consideration. The stress calculation formula for deep beams is deducted, which provides a simple and precise calculation method that can be easily achieved in engineering design.